Warning - probable dumb question on maximum apertures

[davidedric]

Hi,

When I started taking photographs a long, long time ago, maximum lens aperture was crucial because film speed were limited, and the quality started to fall off seriously above 200 ISO (I used to shoot slide film), and we didn't have image stabilisation. So a wide aperture was pretty essential to get decent images, especially for wildlife stuff.

Now we have such a massive range of ISO's available, at least at the fast end, does it really make that much difference? Now I can set the aperture to give the best sharpness for the lens, for example, set a shutter speed appropriate for the focal length and type of shot, and let the ISO take care of the rest. It seems to me that covers the vast majority of shots.

I know there will be very low light conditions where a faster lens could make a difference (the fastest I currently have is 2.8 on a Sigma 17-70mm), but I'm not a professional and paying twice as much for a lot heavier glass doesn't seem worth it, even if the IQ quality is in theory better.

I know I can get a shallower DoF with a faster lens, but again - how often am I really, really going to need that?

While I'm posting is there a thread somewhere that explains why we can't have really low ISO settings in camera (mine's a Canon 600D), to get nice slow shutter speeds without resorting to ND filters?

Thanks for reading and any comments,

Dave

[Dave Humphries]

Hi Dave,

The person here at CiC that makes the best use of wide apertures on telephoto lenses is probably Thierry (tb72) for his showjumping pics.

Beyond that, as you say, I tend to use f/8 for the lens' sweeter spot and use the iso at 400 (sunny) or 800-1600 (dull) to maintain a sensible shutter speed for subject movement and rely on IS to help with camera shake, although I am often at 1/800 - 1/3000 anyway for birds in flight.

As I don't own much fast glass, or live in a 'bright' country, I don't often encounter the lack of ND problem.
Not a dumb question at all, but one I'm gonna dodge

Cheers,

[Scott Stephen]

I might not be understanding the question. You are commenting on how the variable ISO settings enable you to do a lot that in the past, shooting film, you had to accomplish by manipulating aperature and using darkening filters, right?

If that is your point, then I agree that being able to select a range of useful ISO's in-camera (100 to about 800 max with decent IQ in my camera) helps enormously.

I guess though, that it is all about what and where you shoot. You seem to go for the opposite of what I go for. In bright light you are worried about getting a "nice slow shutter" and even using ND filters a lot. You say you don't care much at all about shooting issues in low light, and you also don't place much value on narrow depth of field. I struggle with the opposite, since I often shoot my kids indoors and in poor light, and I shoot informal portraits a lot so I really do want shallow DOF. I wish I could shoot nice shots at 1600 or 3200 or 6400 ISO, but I don't have the big bucks for the body that will do that!

[davidedric]

I guess though, that it is all about what and where you shoot.

Yes, you're right Scott. I should have put that in. I shoot mostly wildlife and landscape. Very little indoors, and very few formal portraits. The slow shutter speeds I would like for blurring moving water, mostly. Hope that makes sense.

The post was prompted by reading quite a lot on here about fast glass, and wondering just how much difference would it make to me, and wondering what others thought.

Thanks for your feedback

[Manfred M]

Dave; the tradeoffs are still there and I am one that prefers fairly fast glass. I'm an old film shooter and know what you are saying. Shooting the slowest film (Kodachrome 25 was one of my all-time favourites) required very good lighting and if I was out shooting existing light, pushing Tri-X to 800 - 1600 gave you useable, albeit grainy results.

Digital sensors are not magic. The lowest ISO settings are going to give you the best quality; i.e. best latitude and lowest noise, so shooting at as slow an ISO as you can get away with still makes sense to maximize image quality. In my view grain in high speed film was a lot more attractive than sensor noise at high ISO settings.

Camera lenses are a lot better than they used to be today as well. High index glass and aspherical lens elements are no longer the exotic components that were only available in the ultra-high end products. Fast glass does have it's disadvantages; cost and weight; but on the other hand, I have yet to hear a photographer complaining about his / her lens being too fast...

[davidedric]

I have yet to hear a photographer complaining about his / her lens being too fast...

True, true - mind you, I've heard a few cursing whilst they carted it up a hill

[Manfred M]

True, true - mind you, I've heard a few cursing whilst they carted it up a hill

Which is why I have two sets of gear. My D800 with the three large and heavy pro lenses are for short hikes (f/2.8 14-24mm; f/2.8 24-70mm and f/2.8 70-200mm). If I am planning to be outdoors walking all day my D90 with the /f3.5 - f/5.6 18-55mm and f/4.5-5.6 55-200mm lens will be in my backpack.

If I am out shooting wildlife the wide angle lens will get left behind and either the 80-400mm or 150-500mm are along instead.

[John Morton]

I have one piece of fast glass that I am really happy with, and am very glad I purchased it. It's the AF-S Nikkor 50mm f/1.4G, and I'll throw it on my D700 when I am going to be shooting indoors in situations where I won't be using a flash.

It's a great 'walking around' lens, too (as an old film shooter who stared with the standard 50mm lens) but it is really great for indoor concert photography, where use of a flash is distracting/invasive to the people on stage and the use of a tripod is impossible due to the attending crowd. Even with high ISO ratings, a decently fast shutter speed is still a must; and that often means as fast a lens as is practical.

[krispix]

A fast lens (i.e. large aperture) is about two things. First, lenses are rarely at their best at either end of the aperture range, so if you have a slow lens, say f4, you could be looking at f8 before you start getting into the lens' best range. However, with a f1.4 an aperture of f2.8 could give acceptable results.
Secondly, and probably most importantly, is the amount of light it will let in while you're focusing and arranging your shot. Try setting your lens to f11 and then hitting the preview button and you'll get an idea of what this can mean. I know we all have autofocus these days, but the camera still needs good, bright, contrasty images to focus accurately and quickly.
I don't know what camera/lens setup you've got, but I've just experimented with my 50mm f1.4 and 200mm f5.6. The 50mm snaps into focus a great deal quicker than the 200mm.

[davidedric]

Thanks, everyone. Feeling a bit overwhelmed...........

But can anyone answer my other question: why don't we have low ISO speeds available?

I thought they could be useful, but maybe I'm missing things.

[dje]

Thanks, everyone. Feeling a bit overwhelmed...........

But can anyone answer my other question: why don't we have low ISO speeds available?

I thought they could be useful, but maybe I'm missing things.

Dave I think it comes down to sensor saturation. While the shutter is open, the charge on each sensor pixel builds up to a certain point depending on the light level on each pixel. For a "good exposure", the brightest pixels will be close to saturation point on the sensor.If the exposure is reduced, this can be compensated by a higher ISO (amplication of the analogue output of the sensor). However if the exposure were increased, the brightest pixels would go into saturation and any "attenuation" applied after the sensor analogue output would not be able to fix this.

I believe the high end Canon's have a setting which allows you to go from ISO 100 down to ISO 50 but they use some fancy processing to achieve this. Colin might be able to help with this as I think he has commented on it before.

Dave

[dubaiphil]

The biggest boon for me, moving to a D700 just over a year ago, was the high ISO capability relative to my D90. I don't have a lot of nature or wildlife to shoot here in Dubai but I had the chance over the past year to shoot at some sporting events - these events are generally held in the evening with varying levels of light as the sun sets and the artificial light takes over. Also being sport, I wanted fast shutter speeds to freeze motion (and in some cases freezing sand as it was thrown about at beach soccer so very high shutter speeds).

For the beach soccer, the pro that was shooting the event for the organisers (I want his job!) was using a D3 and 400mm f2.8 lens, combined with a D3 and 70-200mm f2.8 lens. That was giving him great shallow depth of field and sharpness and as it was his paid day job you can see the justification for it.

My only long lens is a variable aperture 70-300mm - good in daylight on the D90 but useless in low light because of the ISO constraints of the D90 body. All of a sudden it was very useful on the D700, capturing some great shots stopped down a little from wide open. Sure, the depth of field wasn't so shallow or the backgrounds as creamy, but it did the job. So for me, and what I shoot, I couldn't see the value in dropping $10,000 for a 400mm f2.8 or even a 70-200mm f2.8. If you really really want the shallow depth of field look with cheaper glass you can always look down the software option as well, of course, with plug ins like Alien Ware Bokeh.

I tried using some different lenses at sporting events as well, using the 85mm f1.4 at around f1.8 to f2. Even though it is a relatively slow focusing portrait lens it produced some great results and I've noticed on the website for the beach soccer that the photographer has started using some wider glass to shoot his events now too.

So for me too, I can't justify dropping a large amount of $$$ on a fast tele, much as I'd love to. If things change in the future and I'm covering sports events more often and/or getting paid to do so then I might reconsider but otherwise I'm happy with my lot.

Another negative with going the high ISO route though is colour. Different bodies create different results, but colour saturation and accuracy will drop with higher ISOs and so if you're shooting with a slower lens you'll have to account for that.

[jcuknz]

After years of being used to having an f/2.8 or f/3.2 at the end of my zoom I baulked at replacing with just an f/5.6 until I decided that a bigger sensor size compensated, enabled a higher ISO, when I went from bridge to M4/3. In practice being able to use 640ISO instead of just 100 ISO compensates for the 'dreadful' f/5.8 of my current lens. I could use my old f/1.4 50mm lens manually but have yet to do this, even for practice. There is also the consideration of how much one can lift an image in editing ... two or three stops without undue loss of IQ ....I appreciate that some may want to photograph black cats in the coal celler .... but not me

[OldFrank]

The limit on how low the ISO can go is likely limited by the maximum light level the sensor can handle. The ISO setting is the electronic gain used following the sensor. As the actual light falling on the sensor increases it will eventually reach a point where the sensor starts to saturate and clip. The situation is similar to the audio inputs on a camera where feeding line level to a mike level input produces severe distortion even if the audio mixer gain is turned down.

Hope this makes some sense.

[Scott Stephen]

Yes, you're right Scott. I should have put that in. I shoot mostly wildlife and landscape. Very little indoors, and very few formal portraits. The slow shutter speeds I would like for blurring moving water, mostly. Hope that makes sense.

The post was prompted by reading quite a lot on here about fast glass, and wondering just how much difference would it make to me, and wondering what others thought.

Thanks for your feedback

Well... if you REALLY don't shoot indoors or at dusk or anything like that, then you can save a lot of money buying less bright glass (f/4 something for shorter lenses, or f/5.6 or so for longer glass). The wider aperature lenses cost a LOT, and you can save on the narrower ones.

Personally I would go for less-bright glass on the long lenses which you will probably only use OUTDOORS and in bright daytime anyway. Save a ton.
I WOULD be sure to own at least one lens that is good at short range in lower light. A fixed length (Prime) would be ideal. They are small, light, bright and cheap. You could get a 50mm or a 35mm lens with an aperature wider than 2.0 for not a lot of money, and it could save you on those few occasions when you DO need a shot indoors with only average-to-dim light!
Good luck!

[rpcrowe]

Let me provide my opinion...

Fast f/stops... The combination of today's high ISO capabilities will negate (to a degree) the absolute need for very fast maximum f/stops. I also remember when ASA (precursor to ISO and equal in numeric designation) capability of films were much lower than the high ISO capabilities of today's DSLR cameras. Photographers needed faster lenses but, sadly these were not often available and when they were available, they were very pricey. We just made do with what we had!

I shoot with a 17-55mm f/2.8 IS lens paired with a 70-200mm f/4L IS. These two lenses are virtually all I need for a large percentage of my shooting. The 17-55mm f/2.8 IS lens is actually, IMO, a better low light lens than the Canon 50mm f/1.8 Mk-I or Mk-II which is over a stop faster.

The IS capability of the 70-200mm f/4L IS lens allows me to shoot in relatively low light levels. I certainly understand that IS doesn't stop subject motion but, I am not always shooting fast moving subjects and when I do, I will often try to shoot at "peak action" when possible. The f/4 aperture of my 70-200mm f/4L IS lens will, when I am shooting at longer focal lengths be able to provide selective DOF. The rounded aperture blades of the f/4L IS lens also provide very creamy bokeh.

BTW: my 70-200mm f/4L IS lens is not only considerably less expensive than the present f/2.8 IS ii offering, it is also far lighter in weight. I can carry my f/4L IS lens and an extra 1.6x camera at the weight of a 70-200mm f/2.8L (series) lens alone...

I agree with Phil about the necessity for wide f/stops in sports work. One of the standard sports setups for professional shooters is a pair of 1D (series) cameras with the 400mm f/2.8L IS and 70-200mm f/2.8L IS ii lenses. Undoubtedly, this is an excellent setup and if I were a professional sports photographer, I would be shooting with that combination. However as a non-paid occasional sports photographer, I can do very well shooting with 7D and 40D cameras wearing the 70-200mm f/4L IS and 300mm f/4L IS lenses. This is, IMO, the poor (well not so poor) man's sports setup!

As far as slower ISO speeds in DSLR cameras, the answer in simple.... SLOW ISO WON'T SELL CAMERAS. Gazillion ISO capability and umpteen billion pixels, combined with video and articulating viewfinders are the hot commodities now!

[davidedric]

SLOW ISO WON'T SELL CAMERAS. Gazillion ISO capability and umpteen billion pixels, combined with video and articulating viewfinders are the hot commodities now!

Ah yes too true. As they say, follow the money. Many thanks for such an interesting and informative post.

[Cloneranger]

Thanks, everyone. Feeling a bit overwhelmed...........

But can anyone answer my other question: why don't we have low ISO speeds available?

I thought they could be useful, but maybe I'm missing things.

The ISO on my camera goes down to 50. (Sony a77)